Breathable laminates have been used in a variety of applications, and have advantageously been used for wallcoverings. Being “breathable” (also referred to as permeable) refers to the ability of an article or object (e.g., a material) to allow air and/or moisture vapor to be transmitted therethrough, whether the article or material is permeable or semipermeable, including but not limited to the ability to selectively transmit, conduct, or transport gases, mists and vapors of chemicals, and mixtures thereof. Breathable wallcoverings can, for example, be used in relatively humid environments such as bathrooms, kitchens, hospitals, etc., to help prevent or reduce growth of mold and mildew. Wallcoverings include virtually any type of coverings applied to walls for decoration, scrubbability and/or to hide imperfections.
Polyvinyl chloride (PVC), also referred to as vinyl, is commonly used in breathable wallcoverings and many other articles because it is inexpensive. PVC is a thermoset and thus rigid. Thus, addition of a softener, such as a plasticizer (e.g., di-n-octyl phthalate (DNOP), di(2-ethylhexyl) phthalate (DEHP), etc.) is needed to enable PVC to become less rigid. The more the flexibility desired (e.g., in applications such as wall coverings, household articles like shower curtains, medical tubing, etc.), the greater the quantity of plasticizer that must be added to the PVC. Additives to PVC, such as plasticizers, can comprise up to 60-80% of the total weight of a PVC product. Both PVC and its plasticizer, however, have disadvantages and harmful problems associated with their use, and these issues are magnified as the quantity of PVC and/or plasticizer increases.
One problem is that the additives to PVC do not always stay bound to the PVC. Additives can be lost to the air, washed out, consumed by microbes, and/or pass into other materials by direct contact. For example, depending on the temperature, PVC can give off chlorine, a gas that is generally harmful to humans. Stabilizers can be added to the PVC in an attempt to reduce this, but the stabilizers themselves can be consumed. In addition, PVC is not breathable and, as it ages, can emit gases (e.g., chlorine) and can be subject to cracking. Over time, the chlorine and/or plasticizer can leach out, leaving a brittle shell that shrinks and cracks. Further, at moderately high temperatures (e.g., heat from the sun, around 130-140 degrees Fahrenheit (F)), PVC can leak hydrochloric acid (HCL). This can cause yellowing of an article (e.g., a wallcovering) in which the PVC is used. PVC thus does not have a good fade resistance. Furthermore, when chlorine is “liberated” from the PVC, it can cause white PVC to turn black.
Still another issue is that although PVC by itself doesn't burn easily, many of its phthalate-based plasticizers do. Further, because phthalate molecules are not chemically bound to the polymer where they are used as plasticizers, a significant migration of phthalate into the surrounding environment and/or other materials is possible. This is problematic because phthalates have been found to be harmful. For example, the U.S. Department of Health and Human Services National Toxicology Program classifies DEHP as “reasonably anticipated to be a human carcinogen,” and the European Union has determined that DEHP is toxic to reproduction and is banning its used in applications such as toys. In addition, although less is known about the plasticizer DNOP, DNOP still has been found to be a toxin in some situations and, like other phthalates, has been found to be harmful to some populations, such as pregnant women and individuals with respiratory disorders. DNOP also has been found to be harmful to the environment and its ecosystems.
For over thirty years, there has been a concern about excessive amounts of both vinyl chloride and PVC and their plasticizers present at excessive levels in public buildings where frequent washing and disinfecting are necessary, such as hospitals, nursing homes and office buildings. As detection methods have improved, easily measurable quantities of harmful materials such as chlorine gas and HCL have been documented in the air of structures in which PVC articles, especially laminates and wallcoverings, have been installed. Health care professionals have recognized that PVC and its plasticizers present significant indoor air quality issues.
Despite the health issues, cracking, and fading that can occur when PVC is used, there has been resistance to replacing PVC, especially when used in wallcoverings, because of the properties of PVC, including low cost, durability, scrubbability, and fire resistance.